Herrod helpers are 36" wide and 4" deep. The spoiler mounts to the vents without harming the body. The wing doesn't conflict with opening the decklid and can be easily taken off. Honestly though, instead of making one, you should just buy the one from Gilmore Enterprises. I did. The sucker is really well made, built from aluminum and stainless steel. It is really sturdy after everything is bolted down. When I grab & move it, the car moves with it. No flexing. I always thought they were cool when I was a kid ... now I got one! As far as it being detrimental to cooling, I haven't noticed that. However, my volksrod doesn't have much constriction to the fan shroud! It's more like a Baja with a lid.